Marine propeller for discharging engine exhaust through the propeller hub



Oct. 18, 1966 E. c. KIEKHAEFER 3,

MARINE PROPELLER FOR DISCHARGING ENGINE EXHAUST THROUGH THE PROPELLERHUB Filed Feb. 25, 1965 "If j /7 /f 6 7 1 x 20 Z7 7- z :7- 0

I NVENTOR. 52mm CARL llIf/(HAEFER BY & (jiulrus jfdrfi'e Allows UnitedStates Patent 3,279,415 MARINE PROPELLER FOR DISCHARGING EN- GINEEXHAUST THROUGH THE PROPELLER HUB Elmer Carl Kiekhaefer, Winter Haven,Fla., assignor t0 Kiekhaefer Corporation, Fond du Lac, Wis., acorporation of Delaware Filed Feb. 25, 1965, Ser. No. 435,181 Claims.(Cl. 115-17) This invention relates to a marine propeller fordischarging engine exhaust through the propeller hub for marinepropulsion devices. More particularly, the invention relates to athrough-the-propeller exhaust system for outboard motors, stern driveunits and the like.

Generally, such propellers have comprised a hollow hub casing memberwhich supports the propeller blades for propelling a boat or othermarine vehicle through the water. Exhaust from the engine is directedrearwardly through the annular casing for discharge into the water. Anexample of such a propeller is disclosed in Alexander Patent No.2,948,252, issued August 9, 1960, entitled, Propeller Hub ExhaustSystem, and assigned to a common assignee.

When marine propulsion units such as that shown in Patent No. 2,948,252are left in the water in a generally vertical position between uses,water fills not only the propeller hub casing, but also flows forwardlyinto the lower portion of the exhaust passage of the lower housing andrises to the level of the water outside the unit. It has been discoveredthat when the motor is started up, some of the water in the housingexhaust chamber and its opening into the hub may not be dischargedrearwardly. Although the amount of remaining water may be small, it isnevertheless undesirable since it may interfere with the exhaust gaseswhich should be completely free to move from the housing into the hub.

The present invention solves the aforementioned problem. Generally, inaccordance with the invention, the rotary hub casing which supports thepropeller blades is formed to provide an internal passage ofcontinuously increasing section rearwardly from the housing exhaustpassage. More specifically, the inner annular walls of the casing areflared radially outwardly from front to rear.

The accompanying drawing illustrates the best mode presentlycontemplated by the inventor for carrying out the invention.

In the drawing:

FIGURE 1 is a side elevation of an outboard motor which incorporates thepresent invention therein;

FIG. 2 is an enlarged central vertical axial section of the lowerportion of the motor which is normally underwater, and showing detailsof the hub exhaust system;

FIG. 3 is an end elevation of the propeller hub unit;

FIG. 4 is a longitudinal section of a casing showing a second embodimentthereof; and

FIG. 5 is a longitudinal section of a casing showing a third embodimentthereof.

As shown in the drawing, the concept of the invention may be applied toan outboard motor having an engine enclosed by a cowl 1, whichissupported at the upper end of a drive shaft housing 2, and a lowernormally submerged underwater unit 3. The engine drive shaft 4 extendsdownwardly through housing 2 into unit 3 and is coupled as by gears 5,to a generally horizontal propeller shaft 6.

Shaft 6 is suitably mounted for rotation in the lower housing portion 7of unit 3 and extends rearwardly through a threaded opening 8 in housingportion 7. A spool-shaped annular member 9 serves as a central supportfor shaft 6. Member 9 has an annular flange 10 3,279,415 Patented Oct.18, 1966 which is mounted in opening 8, with the flange being providedwith a plurality of circumferentially spaced openings 11 which permitrearward discharge of exhaust gases from an exhaust passageway 12leading downwardly through housing portion 7 from the engine. Such gasesare thus directed through opening 8 of housing portion 7.

An annular retaining ring 13 is threaded into opening 8 and abuts flange10. Ring 13 is adapted to receive the forward end portion of a propellerassembly 14. As shown, assembly 14 comprises a central sleeve 15 mountedon the rear end of propeller shaft 6 by an intermediate rubber drivemember and secured as by a nut 16. A plurality of circumferentiallyspaced longitudinally straight struts 17 extend radially and generallytangentially outwardly from sleeve 15 and support an annular outer hubmember or casing 18 which is concentric with sleeve 15. A plurality ofpropeller blades 19 extend outwardly from casing 18. The casing itselfextends rearwardly substantially beyond the blades.

During operation of the engine of the outboard motor, shaft 4 drivesshaft 6 which in turn rotates propeller assembly 14 to propel the motorand its associated vehicle through the water. During such movement,exhaust gases from the engine will pass downwardly through passage 12,through openings 11 disposed in flange 10, and hence through the hollowcasing 18 of the hub to be discharged into the slip stream of thepropeller.

Since the underwater unit 3 is normally submerged, the water which fillsthe inside of housing 7 should be displaced during operation to providefor freedom of movement of exhaust gases from passage 12 throughopenings 11 and hub casing 18. In accordance with the present invention,means are provided to cause all of the Water disposed adjacent andrearwardly of the housing opening to be fully discharged through thepropeller hub.

For this purpose, and as best shown in FIG. 2, hubcasing 18 is formed tohave an internal annular wall or surface 20 which is straight and whichflares or diverges radially outwardly from near the front end thereofand throughout the major portion of its length. Surface 20 is shown asbeing frusto-conical, and expands continuously from front to rear sothat each circumferential portion thereof is of a larger diameter thanany portion disposed forwardly thereof. When the propeller is rotated,either in a forward or reverse direction, centrifugal force will causeall water within hub casing 18, from opening 8 to the rearmost portionthereof, to flow radially outwardly and rearwardly. Since the outwardlydiverging surface 20 provides a rearward component of force when theradially outwardly moving water impinges on it, the water will flowrearwardly and out of the casing. No pocket of water can form within thehub of the propeller since there are no converging surfaces on theinterior of casing 18. In addition, water in the passageway 12 and inthe vicinity of openings 11 will be drawn away therefrom. The rearwardflow of exhaust gases will be completely free of obstruction by waterand will be initially aided by the vacuum effect of the dischargingwater.

The propeller hub casing shown in FIG. 2 is of uniform thickness andthus has an outer surface 21 which is also frusto-conical and whichdiverges continuously from front to rear. This slight taper of the outercasing surface prevents cavitation in the vicinity of propeller blades19 by densifying water in this region. Propeller efiiciency is thereforeincreased.

Second and third embodiments of a hub casing are shown in FIGS. 4 and 5and are also constructed in accordance with the principles of thepresent invention. In the embodiment of FIG. 4, the inner surface of thecasing 22 is provided with a curved flare and the rate of flare variesby increasing from front to rear, as contrasted with a continuous rateof flare of casing 18. In the embodiment of FIG. 5, the inner surface ofthe casing 23 is also provided with a curved flare, but the rate offlare varies by decreasing from front to rear. In both embodiments,however, the circumference of each section of the inner surfaceincreases rearwardly. In addition, casings 22 and 23 are shown as havingwalls of uniform thickness so that the outer surfaces thereof follow thecontour of the inner surfaces, as in the embodiment of FIG. 2.

The structure of the invention increases the efiiciency of marinepropulsion devices in a simple, yet important manner.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims and particularly pointing outand distinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. A reversible propeller unit for an internal combustion engine drivenmarine propulsion device in which the exhaust gases are dischargedrearwardly through the hub of the propeller, comprising:

(a) a sleeve for mounting upon a drive shaft extending rearwardlythrough the exhaust discharge opening of a hollow underwater unit of thedevice,

(b) a hollow hub casing concentric with said sleeve and spacedtherefrom,

(c) a plurality of spaced longitudinally straight generally radialstruts disposed generally tangential to said sleeve and extending fromsaid sleeve to said casing,

(11) and propeller blades extending outwardly from said casing,

(e) said casing having a continuously rearwardly flared inner surfacewith its smaller end adapted to be disposed adjacent the housing exhaustopening and with its larger end extending rearwardly of said blades.

2. A reversible propeller unit for an internal combustion engine drivenmarine propulsion device in which the exhaust gases are dischargedrearwardly through the hub of the propeller unit, comprising:

(a) a sleeve for mounting upon a drive shaft extending rearwardlythrough the exhaust discharge opening of a hollow underwater unit of thedevice,

(b) a hollow hub casing concentric with said sleeve and spacedtherefrom,

(c) a plurality of spaced longitudinally straight generally radialstruts disposed generally tangential to said sleeve and extending fromsaid sleeve to said casing,

(d) and propeller blades extending outwardly from said casing,

(e) said casing having a frusto-conical outer surface with its smallerend forward of said blades and its larger end rearwardly of said blades.

3. For use with a marine propulsion device having a hollow underwaterhousing with a rearwardly directed engine exhaust opening therein, drivemeans disposed within said housing and extending through said opening: arotatable reversible propeller unit secured to said drive means, saidpropeller comprising:

(a) a hollow annular hub casing adapted to be disposed at its forwardend adjacent said housing opening to provide for free discharge ofexhaust gases therethrough,

(b) propeller blades extending outwardly from said casing,

(c) and means for connecting said casing to said drive means to providerotation thereof, said connecting means including a sleeve and aplurality of longitudinally straight struts disposed tangential to saidsleeve and extending from said sleeve to said casing,

(d) s d hub casing having a curved rearwardly flared surface forming theinner wall of said casing and diverging radially outwardly at a varyingrate and continuously throughout its length from closely adjacent saidhousing opening and rearwardly to the end of the casing to causedischarge by centrifugal force of all water disposed in said casingduring rotation thereof in either direction.

4. For use with a marine propulsion device having anunderwater housingwith an engine exhaust opening therein, and having drive means disposedwithin said housing adjacent said opening: a rotatable reversiblepropeller assembly for attachment to said drive means, said assemblycomprising:

(a) a hollow annular hub casing adapted to be disposed at its forwardend adjacent said housing opening to provide for free discharge ofexhaust gases therethrough,

(b) propeller blades extending outwardly from said casing,

(c). and means for connecting said casing to said drive means to providerotation thereof, said connecting means including a sleeve and aplurality of longitudinally straight struts disposed tangential to saidsleeve and extending from said sleeve to said casing,

(d) said casing having a generally frusto-conical surface forming theinner wall of said casing and diverging radially outwardly continuouslythroughout its length from closely adjacent to said housing opening andrearwardly to the end of the casing to cause discharge by centrifugalforce of all water disposed in said casing during rotation thereof ineither direction,

(e) said casing being of uniform thickness to thereby form acontinuously radially outwardly flared frustoconical outer surface whichtends to prevent cavitation in the area of said blades.

5. For use with a marine propulsion device having an underwater housingfor an engine exhaust opening therein,

and having drive means disposed within said housing adjacent saidopening; a rotatable reversible propeller unit for attachment to saiddrive means, said propeller comprising:

(a) a hollow annular hub casing adapted to be disposed at its forwardend adjacent said housing opening to provide for free discharge ofexhaust gases therethrough,

(b) propeller blades extending radially from said cas- (c) and means forconnecting said casing to said drive means to provide rotation thereof,said connecting means including a sleeve and a plurality oflongitudinally straight struts disposed tangential to said sleeve andextending from said sleeve to said casing,

(d) said casing having a frusto-conical inner surface for the majorlength of said casing and extending -to the rear end thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,614,091 1/1921Van Toff 230-420 2,330,622 9/1943 Ramshorn l66 3,092,135 6/1963Alexander 11s 17 3,102,506 9/1963 Kiekhaefer 11s 17 FOREIGN PATENTS162,066 4/1921 Great Britain.

MILTON BUCHLER, Primary Examiner.

ANDREW H. FARRELL, FERGUS S. MIDDLETON,

Examiners.

1. A REVERSIBLE PROPELLER UNIT FOR AN INTERNAL COMBUSTION ENGINE DRIVENMARINE PROPULSION DEVICE IN WHICH THE EXHAUST GASES ARE DISCHARGEDREARWARDLY THROUGH THE HUB OF THE PROPELLER, COMPRISING: (A) A SLEEVEFOR MOUNTING UPON A DRIVE SHAFT EXTENDING REARWARDLY THROUGH THE EXHAUSTDISCHARGE OPENING OF A HOLLOW UNDERWATER UNIT OF THE DEVICE, (B) AHOLLOW HUB CASING CONCENTRIC WITH SAID SLEEVE AND SPACED THEREFROM, (C)A PLURALITY OF SPACED LONGITUDINALLY STRAIGHT GENERALLY RADIAL STRUTSDISPOSED GENERALLY TANGENTIAL TO SAID SLEEVE AND EXTENDING FROM SAIDSLEEVE TO SAID CASING, (D) AND PROPELLER BLADES EXTENDING OUTWARDLY FROMSAID CASING, (E) SAID CASING HAVING A CONTINOUSLY REARWARDLY FLAREDINNER SURFACE WITH ITS SMALLER END ADAPTED TO BE DISPOSED ADJACENT THEHOUSING EXHAUST OPENING AND WITH ITS LARGER END EXTENDING REARWARDLY OFSAID BLADES.